1. Field of the Invention
The present invention generally relates to a lamp unit. More specifically, the present invention relates to a lamp unit for a liquid crystal display device.
2. Background Information
Electronic devices, such as liquid crystal display devices provided to portable personal computers or the like, are equipped with a liquid crystal display panel and a backlight mechanism. The backlight mechanism is disposed over the liquid crystal display panel. The backlight mechanism generally includes a cold cathode unit (e.g., lamp unit) and a flat light guide plate. The cold cathode unit has a cold cathode tube as a light source. The flat light guide plate guides light from the cold cathode tube to the liquid crystal display panel. The cold cathode unit is disposed facing one end face of the light guide plate. The cold cathode unit is provided so that the light from the cold cathode unit is guided through the light guide plate to the liquid crystal display panel. The cold cathode unit further has a pair of lamp cables, a pair of lamp sockets and a metal lamp reflector. The lamp cables are electrically connected to both ends of the cold cathode tube to supply electrical power to the cold cathode tube. The lamp sockets support the ends of the cold cathode tube. The lamp sockets are mounted to the lamp reflector. The lamp reflector is formed in a reflective film type or a reflective plate type. The lamp reflector of the reflective film type has a substantially U-shaped cross section. The lamp reflector is open only on a side facing an end face of the light guide plate and surrounds the cold cathode tube (e.g., a discharge tube). The lamp reflector reflects light from the cold cathode tube on the U-shaped inner face of the reflective film to illuminate the light guide plate. The lamp reflector of the reflective plate type reflects light from the cold cathode tube by an aluminum plate or another such reflective plate to illuminate the light guide plate. The lamp reflector is provided so that light from the cold cathode tube is incident on the light guide plate either directly or after being reflected by a reflective film, and is guided to the entire liquid crystal display panel surface by the light guide plate. The liquid crystal display devices are utilized as display devices in computers, portable information terminals, portable telephones, television sets, and so forth since the liquid crystal display devices consume less power and are thinner and lighter in weight.
One of the two lamp cables connected to the cold cathode tube passes through a rear side of the lamp reflector (the side where the cold cathode tube is not present). The lamp cable is routed around to the other lamp cable (the other lamp socket). The lamp cable routed in this manner is fixed on the rear side of the lamp reflector so it will not get in the way during assembly of the backlight mechanism, etc. The following means is employed for this fixing.
For example, with one commonly employed means, the lamp cable is fixed to the rear side of the lamp reflector by adhesive tape (such as double- or single-sided tape). Furthermore, a plastic cable holder is attached to the rear side of the lamp reflector to fix the lamp cable to the cable holder. However, this means requires a new member (the cable holder), and therefore increases the number of parts, and furthermore, requires the work of attaching the cable holder. Thus, more processing time is entailed, and this drives up the cost.
Japanese Laid-Open Patent Application Publication No. 2004-212574 discloses a technique of providing a means for fixing a lamp cable to a lamp socket. The technique of Japanese Laid-Open Patent Application Publication No. 2004-212574 will now be described.
A lamp socket is mated to a lamp reflector. A lamp cable is supported by a protrusion provided to the lamp socket. A cold cathode tube is inserted into and supported by a rear face of an insertion hole on an inner face side of the lamp socket mated to the lamp reflector. The lamp cable is connected to one end of the cold cathode tube from the opposite side as the insertion hole and is routed to a rear face side of the lamp reflector. The lamp cable is inserted and supported in an opening. A convex component is provided to the opening of the protrusion on an outside of the opening. The lamp socket is made from rubber, silicone, or another such elastic material. Thus, when the lamp cable is inserted into the lamp socket, the opening is held open by elastic force. When the lamp cable has been housed on the convex component, the opening is closed again by the elastic force. This configuration prevents the lamp cable from coming out of the opening.
With the technique described in Japanese Laid-Open Patent Application Publication No. 2004-212574, the lamp cable is prevented from falling out by providing the convex component to the opening of the protrusion. However, since the protrusion sticks out from the lamp reflector, the opening opens up after the elastic material of the lamp socket changes and deteriorates over time. As a result, the lamp cable comes loose. In particular, in recent years there is more concern about environmental issues. When parts are replaced in a liquid crystal display device, rather than replacing an entire backlight mechanism, the user replaces just the lamp and the lamp cable connected to the lamp. These parts are the parts most likely to deteriorate over time and to affect brightness, which is a measure of the quality of the liquid crystal display device. Therefore, in replacing the lamp and the lamp cable, the opening for supporting the lamp cable is degraded by opening and closing every time the lamp cable is pushed into and pulled out of the lamp socket, and ends up being opened further. The opening is further opened up by changes over time to the material of the lamp socket. Thus, the lamp cable comes loose from the opening. As a result, when the lamp unit is attached and removed, the lamp cable that has come out of the lamp unit contacts with the other constituent members of the backlight mechanism, and damages the backlight mechanism.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved lamp unit. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.